If you want to use photoshop, just set it as your external editor in the iPhoto preferences. Then when you choose a photo and click to edit, PS will open, you can edit and the photo will be saved right back where it ought to be.
iPhoto organizes its files so that the program can work. Users are not meant to muck about in the finder. Corruption and loss of photos will ensue. iPhoto is brilliant about what it does -- it is an organizational and viewing tool. Does its job wonderfully. There is never a need to go into the library in finder. You will have a much better experience is you will simply forget that that file is there and do anything to/with your photos from the app itself. It really is a great program -- simple to use, and once you get the hang of it, could not be more versatile!
Give it another try, forget about the file in finder and see what happens. It truly is brilliant for what it does and is meant to do.